Autonomic Nervous System

Dr. Sama-ul-Haque

Objectives

• Define autonomic nervous system.

• Describe sympathetic and parasympathetic nervous system.

• Enumerate the functions of sympathetic and parasympathetic nervous system.

• ANS is the subdivision of the peripheral nervous system that regulates body activities that are generally not under conscious control

• Visceral motor innervates non-skeletal (non-somatic) muscles

• Composed of a special group of neurons serving: – Cardiac muscle (the heart)– Smooth muscle (walls of viscera and blood vessels)– Internal organs– Skin

The Autonomic Nervous System

Basic anatomical difference between the motor pathways of the voluntary somatic nervous system (to skeletal muscles) and those of the autonomic nervous system

• Somatic division:– Cell bodies of motor neurons reside in CNS (brain or spinal

cord)– Their axons (as nerves) extend all the way to their skeletal

muscles.

• Autonomic system: chains of two motor neurons– 1st = preganglionic neuron (in brain or cord)– 2nd = gangionic neuron (cell body in ganglion outside CNS)

• Axon of 1st (preganglionic) neuron leaves CNS to synapse with the 2nd (ganglionic) neuron.

• Axon of 2nd (ganglionic) neuron extends to the organ it serves

Diagram contrasts somatic (lower) and autonomic:

autonomic

somatic

this dorsal root ganglion is sensory

Divisions of the autonomic nervous system

• Parasympathetic division• Sympathetic division

Serve most of the same organs but cause opposing or antagonistic effects

Parasympathetic: routine maintenance“rest &digest”

Sympathetic: mobilization & increased metabolism “fight, flight or fright”

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Where they come from

ParasympatheticCraniosacral

SympatheticThoracolumbar

T1 to L2

Paravertebral Ganglionic chain or

Sympathetic Trunk

Paravertebral Ganglionic

chain

Spinal Nerve

Sympathetic nerve

Sympathetic Nervous system

Parasympathetic Nervous system

Functions of Sympathetic Nervous System

• Increased Heart Rate• Increased Blood Pressure• Pupil Dilation• Decreased Urination• Increased Sweating• Bronchial Dilation• Decreased Salivation

Functions of Parasympathetic Nervous System

• Decreased Heart Rate• Decreased Blood Pressure• Pupil Constriction• Increased Urination• Decreased Sweating• Bronchial Constriction• Increased Salivation